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56 Cards in this Set
- Front
- Back
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population
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a group of organisms of the same species living in a particular geographic region (small or large)
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evolution
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there was a genetic change in the population
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natural selection
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the consequence of certain individual organisms in a population being born with charactersitics that enable them to survive better and reproduce more than the offspring of other individuals in the population
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darwin's influences
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in the 18th and 19th centuries, scientists began to overturn the commonly held beliefs that the earth was only about 6,000 years old and that all species had been created separately and were unchanging; these gradual changes in scientists' beliefs helped shape Charles Darwin's thinking
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-Georges Buffon
-Georges Cuvier -Jean-Baptiste Lamarck -Charles Lyell |
-earth much older than previously believed
-documenting fossil discoveries, showed that extinction had occurred -suggested living species might change over time -argued that geological forces had gradually shaped the earth and continue to do so |
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Charles Darwin background
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born wealthy in England 1809; studied nature at Cambridge; explored nature and landed job as gentleman companion for captain of ship - 5 year round the world surveying expedition
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what darwin discovered on his trip - species change over time
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noted unexpected patterns among fossils he discovered and living organisms he observed while on the voyage; fossils resembled but were not identical to the living organisms in the same area in which they were found; finch species on each of galapagos islands differed from each other in small but significant ways; observations helped darwin to develop his theory of how species might change over time
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Origin of species
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1859 - alfred russel wallace and him published the joint presentation on their ideas
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section 8.3 (very important)
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evolution can change by 4 different mechanisms
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mutation, genetic drift, migration, and natural selection
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mutation
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an alteration of the base-pair sequence of an individual's DNA and when this alteration occurs in a section of the DNA that codes for a particular gene, the change in the DNA sequence may change the allele.
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what causes mutations?
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incredibly complex process of cell division can go awry; can be induced by environmental phenomena; most occur when DNA of cells is exposed to high-energy sources or mutation-inducing chemicals (mutagens)
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mutation-causing threats
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tanning beds (bombard skin with ultraviolet rays) - greater the incidence of mutations, greater the incidence of mutations and skin cancer
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mutation in the long run
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nearly all mutations reduce an organism's fitness by causing its early death or by reducing its reproductive success
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genetic drift
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a random change in allele freqencies; example: population before genetic drift- allele frequencies (cleft chin-dominant, smooth chin-recessive); reproduction-in this example, a heterozygous couple (Cc) could have 2 children that are homozygous recessive (cc) causing an increase in the proportion of recessive alleles in the population
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genetic drift #2
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population after genetic drift- there are now more recessive alleles in the population than before; fixation-genetic drift leads to fixation when an allele's frequency becomes 100% in population, if this occurs, there is no longer genetic variation for the gene
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impact of genetic drift
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change in allele frequencies is not related to the alleles' influence on reproductive success; impact is much greater in small populations
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fixation
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said to occur when an allele's frequency in a population reaches 100% - if this happens, there is no more variability in the population for this gene; all individuals will always produce offspring carrying only that allele - it reduces genetic variation
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founder effect
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the founding members of a new population can have different allele frequencies than the original source population, and consequently, the new population experiences evolution (amish people)
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population bottlenecks
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occasionally, famine or disease or rapid environmental change may cause the deaths of a large, random proportion of the individuals in a population; remaining members are essentially a random, small sample of the original population
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migration/gene flow
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movement of some individuals of a species from 1 population to another - movement from population to population within a species distinguishes migration from the founder effect, in which individuals migrate to a new habitat, previously unpopulated by that species
= = leads to a change in allele frequencies in a population as individuals move into or out of the population |
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migration process
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1- 2 populations of the same species exist in separate locations (mountain range)
2- a group of individuals from population 1 migrates over the mountain range 3 - the migrating individuals are able to survive and reproduce in the new population |
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natural selection 3 conditions
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1 - there must be variation for the particular trait within a population
2 - that variation must be inheritable (must be capable of being passed on from parents to their offspring) 3 - individuals with one version of the trait must produce more offspring than those with a different version of the trait |
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condition 1: variation for a trait
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variation - it is the raw material on which evolution feeds; variations in physical features, physiological, and biochemical ways too
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condition 2: heritability
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for natural selection to act on a trait within a population, offspring must inherit the trait from their parents
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inheritance/heritability
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transmission of traits from parents to their children through genetic information
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condition 3: differential reproductive success
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1 - more organisms are born than can survive
2 - organisms are continually struggling for existence 3 - some organisms are more likely to win this struggle and survive and reproduce - struggle does not always involve direct physical contact, but in a world of scarce, limited resources, finding food or shelter is a zero-sum game: if one organism is feasting, another is more likely to be starving |
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differential reproductive success
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3 part observation - led Darwin to his 3rd condition for natural selection: from all the variation existing in a population, individuals with traits most suited to reproduction in their environment generally leave more offspring than do individuals with other traits
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natural selection occurs when these 3 basic conditions are met -
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1 - variation for a trait
2 - heritability of that trait 3 - differential reproductive success based on that trait |
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sexual selection
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satisfy the 3 conditions for natural selection, increase in frequency just the same
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8.4
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fitness
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a measure of the relative amount of reproduction of an individual with a particular phenotype, as compared with the reproductive output of individuals with alternative phenotypes
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important elements to an organisms fitness #1
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an individuals fitness is measured relative to other genotypes or phenotypes in the population
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i.e.t. an o.f #2
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fitness depends on the specific environment in which the organism lives
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i.e.t. an o.f. #3
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fitness depends on an organism's reproductive success compared with other organisms in the population - if you have an allele that causes you to be sterile and incapable of producing offspring, your fitness is 0. (whether particular traits increase their market share)
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adaptation
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refers both to the process by which organisms become better matched to their environment and to the specific features that make an organism more fit
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natural selection does not lead to organism's perfectly adapted to their environment because:
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1 - environments can change more quickly than natural selection can adapt organisms to them
2 - all possible allele's are not produced by mutation 3 - there is not always a single optimum adaptation for a given environment |
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artificial selection is a special case of natural selection
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animal breeders and farmers are making use of natural selection when they modify their animals and crops, because the 3 conditions for natural selection are satisfied. since the differential reproductive success is determined by humans and not by nature, this type of natural selection is also called artificial selection
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directional selection
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individuals with 1 extreme from the range of variation in the population have higher fitness
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?
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Lateral condyle of the humerous
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disruptive selection
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example - medium size fish get outcompeted for territory by larger fish. smaller fish are able to sneak in and fertilize eggs before being detected
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natural selection can cause the evolution of complex traits and behaviors
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natural selection can change allele frequencies for genes involving complex physiological processes and behaviors. sometimes a trait that has been selected for one function is later modified to serve a completely different function.
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8.5 - the evidence for the occurrence of evolution is overwhelming
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5 primary lines of evidence demonstrating the occurrence of evolution
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1 - the fossil record (physical evidence that organisms lived in the past)
2 - biogeography (patterns in the geographic distribution of living organisms) 3 - comparative anatomy and embryology (growth, development, and body structures of major groups of organisms) 4 - molecular biology (the examination of life at the level of individual molecules) 5 - laboratory and field experiments (implementation of the scientific method to observe and study evolutionary mechanisms) |
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fossils
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remains - can be used to reconstruct what organisms must have looked like long ago
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radiometric dating
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helps in further painting a picture of organisms' evolutionary history by telling us the age of the rock in which a fossil has been found - makes it possible to figure out absolute age
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radiometric dating made possible by:
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evaluating the amounts of certain radioactive isotopes present in fossils - radioactive isotopes in a rock begin breaking down into more stable compounds as soon as the rock is formed, and they do so at a constant rate - by measuring the relative amounts of the radioactive isotope and the leftover decay product in a rock where a fossil is found, the age of the rock/fossil can be determined
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how old is the earth
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about 4.6 billion years old - earliest organisms appeared at least 3.8 billion years ago
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missing link - tiktaalik
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1st found in canada, estimated to be 375 million years old - seem to represent a transitional phase between fish and land animals; had gills and scales but also had arm like joints similar to seals
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biogeography
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study of the distribution patterns of living organisms around the world
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to help understand evolutionary histories of populations
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observing geographic patterns of species distributions, particularly noting similarities and differences among species living close together but in very different habitats and among species living in similar habitats but located far away
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homologous structures
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similarities in the bone structures of the forelimbs of mammals demonstrate common ancestry - the same with the tail in embryos
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vestigal structures
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homologous structures sometimes come to have little or no function at all - these are the evolutionary leftovers - exist because they value ancestrally (molars in bats even though they consume a liquid diet)
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convergent evolution
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all of the analogous structures developed from different original structures - uses the different starting materials available and modifies them until they serve similar purposes
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molecular biology
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all living organisms share the same genetic code; the degree of similarity in the DNA of different species can reveal how closely related they are and the amount of time that has passed since they last shared a common ancestor
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laboratory and field experiments
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multiply replicated, controlled lab selection experiments and long-term field studies of natural populations - including observations on antibiotic-resistant strains of disease causing bacteria - enable us to watch and measure evolution as it occurs
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